This invention relates to a luminaire and, more particularly, to a luminaire comprising a reflector which, though having a generally symmetrical configuration with respect to its central axis, is capable of producing a photometric distribution of its light output that is asymmetrical with respect to said central axis.
A very cost-effective method for making the reflector of a luminaire is a spinning process in which a disk-shaped blank of metal is spun into a hollow form suitable for the final configuration of the reflector. In a typical spinning process, a mandrel having an external shape corresponding to the internal shape of the reflector being formed is rotated about a central axis while the disk-shaped metal blank, fixed to the mandrel and rotating therewith, is deformed about the mandrel by localized force applied to the blank through a stationary spinning tool. For a more detailed description of such a spinning process, reference may be had to the section on spinning in the American Society of Metals Handbook, published in 1967 by the American Society of Metals, Cleveland, Ohio, pages 201-208, Volume 4.
This spinning process readily lends itself to the manufacture of reflectors that are symmetrical with respect to a central axis since the mandrel and the disk-shaped blank being formed are usually rotated about such axis during spinning. A reflector that is symmetrical about a central axis will ordinarily provide a symmetrical photometric distribution of its light output, assuming the light source of the luminaire is located on the central axis of the reflector. In many lighting applications, however, a photometric distribution that is asymmetrical with respect to the central axis is desired. A lighting application of this type is disclosed in U.S. Pat. No. 4,303,971 - Hogue et al, assigned to the assignee of the present invention, where the disclosed luminaire is used for illuminating stacked material along a warehouse aisle. This luminaire directs most of its light output from the reflector along the length of this aisle, developing four light beams that emanate from the reflector in an elongated X-shaped pattern, as seen in FIGS. 4 and 5 of the patent.
In order to develop this radially asymmetrical light pattern, Hogue is required to rely upon a reflector that is asymmetrical with respect to its central axis. More specifically, his reflector comprises four reflector portions that together surround the central axis of the reflector and are each of an elliptical form when viewed in horizontal cross-sectional planes taken through the reflector. This is a rather complicated configuration, use of which requires that the reflector be formed by some process other than the relatively simple and inexpensive spinning process referred to above. In actual practice, a two-step hydroforming process is relied upon.